1. Field of the Invention
This invention relates to a hot-water type heating apparatus for controlling a hot-water flow quantity using a flow-quantity control valve and regulating temperature of air blown into a passenger compartment which is particularly suitable for use in a hot-water type heating apparatus of an automotive air conditioner.
2. Description of Related Art
An apparatus for controlling a quantity of flow of hot water to a heating-use heat exchanger and controlling blown-air temperature in an automotive-use air conditioner including a hot-water type heating apparatus is known in the art. Because a water pump driven by a vehicle engine is used in an automotive-use air conditioner to circulate hot water (engine coolant) in a hot-water circuit including the above-described heat exchanger, the speed of the water pump fluctuates in tandem with fluctuations in engine speed, and hot-water pressure to the heating-use heat exchanger fluctuates greatly.
This fluctuation in hot-water pressure causes the quantity of hot-water flow to the heat exchanger to fluctuate, and so becomes a factor for causing heat-exchanger blown-air temperature to fluctuate.
In Japanese Patent Application Laid-open No. Hei 8-67128, the inventors proposed a hot-water type heating apparatus for suppressing fluctuations in heat-exchanger blown-air temperature. This apparatus has a heating-use heat exchanger for performing heat exchange between air and hot water supplied from a water-cooled vehicle engine, a flow-quantity control valve for controlling a quantity of hot-water flow supplied to the heating-use heat exchanger from the engine, and a bypass circuit for allowing hot water to flow therethrough while bypassing the heating-use heat exchanger.
Accordingly, a pressure-actuated valve for enlarging a degree of opening of the bypass circuit in correspondence with pressure elevation of hot water supplied from the engine in the bypass circuit is disposed in the bypass circuit so that elevation of differential pressure before and after the heating-use heat exchanger (i.e., increase in quantity of flow of hot water to the heat exchanger) is suppressed by the pressure-actuated valve, and fluctuation in heat-exchanger blown-air temperature is also suppressed.
When the inventors actually constructed a prototype of a valve apparatus (not known in the art) based on the above-described apparatus as shown in FIG. 13 and conducted experimental investigation, when engine speed was varied from idle speed (750 rpm) to a high speed of 6,000 rpm, blown-air temperature of the heating-use heat exchanger fluctuated as shown in FIGS. 8A, 8C and 8E.
Here, .DELTA.Ta is the fluctuation of heat-exchanger blown-air temperature when idling (750 rpm) to a high speed of 6,000 rpm; at flow-quantity control valve degree of opening .theta.=20.degree., 30.degree., or 40.degree., blown-air temperature fluctuation range .DELTA.Ta reaches 7.degree. C. to 15.degree. C. at the hot-water inlet side (1) and reaches 3.degree. C. to 24.degree. C. at the hot-water outlet side (2), and it was determined that a problem occurs wherein controllability of heat-exchanger blown-air temperature deteriorates.
Regarding a cause of occurrence of the foregoing fluctuation in heat-exchanger blown-air temperature, the inventors determined the reasons to be the following via experimental investigation.
First, to describe the overall structure of the prototype device shown in FIG. 13, a flow-quantity control valve 4 has a valve body 13 structured as a rotatable rotor, hot water from an engine passes from a hot-water inlet pipe 19 through a control passage 170 provided on the valve body 13, flows in the direction shown by the X symbol (i.e., into the page), and into a heating-use heat exchanger 3. Hot water flowing out from an outlet of this heating-use heat exchanger 3 is conducted from a hot-water inlet pipe 26 to a housing 14, and after passing through the interior of this housing 14, hot water is returned from a hot-water outlet pipe 28 the engine.
Additionally, when engine speed rises and hot-water pressure becomes higher, a pressure-actuated valve 6 provided in a bypass circuit 5 opens and a portion of hot water from the hot-water inlet pipe 19 passes through the control passage 170 of the valve body 13 and is allowed to escape toward the bypass circuit 5, through which flow quantity of hot water to the heating-use heat exchanger 3 is controlled.
Further, the valve-body 13 control passage 170 is provided with inlet-side opening portions 171 and 171a into which hot water from the hot-water inlet pipe 19 flows, outlet-side opening portions 173 and 173a to cause hot water flowing into these inlet-side opening portions 171 and 171a to flow out toward a hot-water outlet side of the heating-use heat exchanger 3, and a bypass-side opening portion 172 to cause hot water to flow out toward a bypass opening 21 side, and the intervals among these several opening portions communicate with one another via an intermediate passage 174 passing radially through the valve body 13.
Moreover, the inlet-side opening portion 171a is made up of a small circular hole of diameter 2 mm or equivalent for establishing a small hot-water flow quantity.
However, when a mode of hot-water flow in the control passage 170 of the valve body 13 was scrutinized, it was understood that the phenomenon which will be described hereinafter occurred. Namely, in a state wherein the valve body 13 of the flow-quantity control valve 4 is set at a position of a predetermined intermediate degree of opening (for example, degree of opening .theta.=30.degree.) or less, hot water from the hot-water inlet pipe 19 flows into the intermediate passage 174 via the inlet-side opening portion 171a made up of a small circular hole of diameter 2 mm or equivalent of the valve body 13, and moreover, hot water flow out from this intermediate passage 174 passes through the bypass-side opening portion 172 toward the bypass opening 172 side, and along with this, hot water flows out via the outlet-side opening portions 173 and 173a to the hot-water inlet side of the heating-use heat exchanger 3.
At this time, a static pressure component of the hot water is greatly reduced by a throttling effect at the inlet-side opening portion 171a, but because the velocity of hot water sprayed from the inlet-side opening portion 171a is high, a dynamic-pressure component of this sprayed hot water (dynamic pressure is proportional to .rho.v.sup.2, where .rho. is density and v is velocity) assumes a high value and has sufficient energy.
However, in a structure of the control passage 170 in a comparative device, sprayed hot water from the inlet-side opening portion 171a strikes an inner-wall surface of the intermediate passage 174 at a diagonal in a direction opposite the bypass opening 21, as shown by arrow B in FIG. 13, and so main flow of sprayed hot water from the inlet-side opening portion 171a, after having collided with the inner-wall surface of the intermediate passage 174 is directed in a direction opposite to the bypass opening 21.
As a result thereof, a majority of dynamic-pressure energy of sprayed hot water from the inlet-side opening portion 171a does not effectively act upon a valve body 30 of the pressure-actuated valve 6, and so when engine speed has risen and a quantity of hot-water flow from the engine has increased, a lift quantity of the valve body 30 cannot increase up to a position corresponding to the increase in hot-water flow quantity. Owing thereto, the quantity of bypass-side hot-water flow to the bypass circuit 5 cannot be increased to a quantity corresponding to the rise in engine speed, and so the quantity of hot-water flow to the heating-use heat exchanger 3 is increased by a corresponding amount during high speed compared to flow during idling, and blown-air temperature rises.
Additionally, when the inventors actually constructed the prototype valve (not known in the prior art) shown in FIG. 21 and conducted experimental investigation, it was determined that when flow-quantity control valve degree of opening .theta. has reached an intermediate opening-degree position (degree of opening .theta.=approximately 70.degree.), a phenomenon occurs wherein heat-exchanger blown-air temperature declines suddenly, and a problem occurs wherein controllability of heat-exchanger blown-air temperature and in turn passenger-compartment interior temperature deteriorates, as shown in FIG. 22.
Regarding a cause of occurrence of a sudden decline in heat-exchanger blown-air temperature, the inventors, upon discussion via experimental investigation of the prototype device, determined the reasons to be the following.
Namely, when the valve body 13 of the flow-quantity control valve 4 has reached a predetermined intermediate opening-degree position, hot water from the hot-water inlet pipe 19 passes through the inlet-side opening portion 171 and the bypass-side opening portion 172 of the control passage 170 of the valve body 13, and is substantially linearly sprayed to the bypass circuit 5 side at a rapid flow speed, as is shown in FIG. 21.
Here, arrow Y in FIG. 21 shows flow of hot water to the bypass circuit 5 side, and degree of opening .theta. of the valve body 13 in FIG. 21 is 60.degree.. Because the valve body 30 of the differential-pressure valve 6 is disposed adjacently to the valve body 13, the above-described dynamic pressure (jet dynamic pressure) of the sprayed hot water is directly applied to the valve body 30 of the differential-pressure valve 6.
Owing thereto, a lift quantity (degree of opening) of the valve body 30 becomes excessively large, and as a result thereof, flow quantity of bypass-side hot water flowing through the bypass circuit 5 increases. Here, according to experimentation and investigation by the inventors, it was understood that the phenomenon where the lift quantity of the valve body 30 becomes excessively large due to the dynamic pressure of the sprayed hot water occurs markedly under conditions wherein distance L between a valve seat 33 of the valve body 30 and a central position of the valve body 13 is 60 mm or less (in a mode wherein the two valves 4 and 6 are adjacently disposed).
A union portion O where the above-described bypass-side hot water and returning hot water (hot water from the hot-water inlet pipe 26) which has flowed out from the heating-use heat exchanger 3 outlet is disposed on a downstream side of the valve body of the differential-pressure valve 6; the returning hot water from the heating-use heat exchanger 3 outlet is checked at this union portion O due to the flow-quantity increase of the bypass-side hot water, and the quantity of hot-water flow to the heating-use heat exchanger 3 is reduced. It was understood that the sudden decline in heat-exchanger blown-air temperature shown in FIG. 21 occurred as a result of this.